1. Field of the Invention
The present invention relates to improvements of a magnetic recording medium used for a magnetic recording and/or a reproducing apparatus and it particularly relates to a magnetic recording medium employing an anti-mold agent for preventing mold (mildew) from generating in the magnetic medium.
2. Description of the Related Art
Presently, a magnetic recording medium, such as a magnetic tape is constructed by coating a magnetic paint on one side of a non-magnetic base, for instance, a polyester film to form a magnetic layer.
Such magnetic paint generally comprises magnetic particles, abrasive, light blocking agents; binders, for instance, polyvinyl chloride, polyurethane or nitrocellulose; dispersant for promoting dispersion; lubricant for improving tape running characteristic, for instance, fatty acid, fatty ester or silicon oil. The mixture of these materials are kneaded with solvent by a mixer for better dispersion to obtain the magnetic painting. Further, a back coating layer is formed on the other side of the non-magnetic base by coating a carbon black painting for improving the tape running characteristic and the light blocking characteristic.
However, since the additives such as binders and lubricants contained in the magnetic layer (the magnetic painting) or the back coating layer are made of organic compounds, the additives serve as nourishment to mold in the magnetic or the back coating layer. If the mold should adhere to the layers, the magnetic medium may be contaminated by proliferated mold, which may pose a problem of adherence between layers of wound magnetic tape or contamination of a magnetic head which scans the magnetic tape leading to erroneous recording or reproducing of signals.
Japanese Laid Open Patent Application No. 214212/1986 and Japanese Laid Open Patent Application No. 49217/1990 disclose employment of anti-mold agents on the magnetic layers or the back coating layers to prevent mold from generating thereon.
The above magnetic mediums employing the disclosed anti-mold agents indicate anti-mold effects in some degree at initial states, however, it is found that the magnetic mediums lose the anti-mold effects after the magnetic mediums have been repeatedly used.
Further, since the polyurethane and the polyvinyl chloride are liable to generate mold, and the fatty acid is a good nourishment to the mold, the magnetic mediums employing those materials in particular require stronger anti-mold agents.